ERA11GA066

The pilot's inadvertent encounter with an unexpected intense rain shower with severe turbulence at night.

Prior to the flight, the crew attended a mass briefing with the military training exercise personnel for whose operations the flight was to provide aerial support. The briefing included weather forecast information but did not include any indication of rain showers, thunderstorms, or other hazardous weather over the military operations area or near the landing airport for the period of operations. During the flight, the weather in the area began to deteriorate. Other pilots, ground personnel, and witnesses reported periods of heavy rain and reduced visibility. Infrared satellite imagery for the time period of the accident flight depicted an area of cumulus congestus cloud development over south-central Florida, north of a stationary frontal boundary, moving north. Ground personnel were monitoring the deteriorating weather as the accident airplane continued its mission. Although there may have been discussions of a weather recall, the evidence indicates that this did not occur. The accident pilot likely discontinued his mission and initiated a return to the airport due to the weather conditions. The airplane was not equipped with weather radar. As the airplane approached the airport from the north in night conditions, it encountered the edge of an area of echoes with a maximum core reflectivity of 55 decibels; such echoes are capable of producing severe turbulence and strong outflow winds. The right wing separated in flight, and the airplane crashed inverted in a farm pasture west of the airfield. An examination of the wreckage did not reveal evidence of a preexisting mechanical malfunction or failure. All observed fracture surfaces on the right wing showed indications of overstress.

HISTORY OF FLIGHT On November 17, 2010, about 2050 eastern standard time, a Cessna M337B, N1309, impacted terrain following an in-flight separation of the right wing near Avon Park, Florida. The airplane was registered to a private individual and the public use flight was operated by Patriot Technologies LLC under contract with the Department of Defense. The commercial pilot and two pilot-rated crewmembers were killed. Night instrument meteorological conditions were present in the area, and no Federal Aviation Administration (FAA) flight plan was filed. The local flight originated at MacDill Air Force Base Auxiliary Field (AGR), Avon Park, Florida, about 1932. According to the operator, the purpose of the flight was to provide aerial support to an Air Force Special Operations Command (AFSOC) training exercise. The flight, using call sign "Jedi 21," was in contact with AGR tower at the time of the accident. Tower instructed Jedi 21 to report a two-mile final for runway 5. When Jedi 21 did not report final, a search and rescue response was initiated. The wreckage was located about 0118 on November 18. Several Department of Defense personnel were on the Avon Park Air Force Range at the time of the accident. These persons included range and airspace controllers, a weather forecaster, and other flight crews. An Air Force Staff Sergeant, acting as a primary Restricted Operating Zone (ROZ) controller, reported the following. Jedi 21 checked in on station and worked on his frequency for about an hour, until he reported a "bent sensor." According to the operator, "bent sensor" is an Air Force Tactics, Techniques, and Procedures Manual 3-1 standard communication term indicating a technical anomaly with sensor equipment. The ROZ controller continued to work with Jedi 21 for about 30 more minutes before checking off station uneventfully. An Air Force Tech Sergeant, also working ROZ controller duties, reported the following. About 2040, he received a call from Jedi 21 stating that the flight was returning to base (RTB). The controller requested the reason for the RTB, and reportedly received no response from Jedi 21. The controller further stated that they were tracking weather in the area to determine if returning other flights to base was warranted. About 15 minutes later, or about 2055, AGR tower called him and inquired as to the location of Jedi 21. The controller believed at the time that Jedi 21 had landed. About the same time, the "…weather conditions became severe at AGR with heavy rain and limited visibility." An Air Force Staff Sergeant, performing communications link duties between range control, AGR tower, and ROZ control, reported the following. He heard the RTB call from Jedi 21 to the ROZ controller. When the controller asked for the reason for the RTB, no response was heard. About 2045, Jedi 21 called "inbound to Avon Aux Field (AGR)." He then heard Jedi 21 call 4 miles from AGR, which was the last radio call he heard from Jedi 21. He added that, about 2055, the "weather significantly grew worse with heavy rain at the Avon Field." An Air Force Staff Sergeant, performing weather forecaster duties, reported the following. He began to prepare for the 1830 evening mass briefing about 1500, and stated, "...conditions looked to be on track with relatively clear skies." He recalled that, before the mass briefing, mid-level cloud cover increased at around 7,000 to 8,000 feet with some scattered clouds to the south at about 4,000 feet. He noted some weak returns on the radar to the south but felt that they would "die out relatively quickly" with the loss of heating as the evening progressed. His overall assessment of the synoptic situation and weather on the night of the accident is that "there was no significant weather event during the operation other than a brief heavy shower." He also stated that the showers did not occur until after communication was lost with the accident airplane. In a timeline attached to his written statement, the forecaster reported that between 1930 and 2000, he continued to monitor weather to the south and could see showers continuing to "back build" on radar to the southwest, tracking northeast. He notified exercise command of a possible recall of light and medium fixed wing aircraft and requested a pilot report from the south ROZ with no response. About 2010, he received a pilot report of 3,000 foot ceilings and rain to the south. During the time period of 2015 to 2030, he contacted tower to recommend a recall of visual flight rules (VFR) aircraft due to worsening conditions with rain and lowering ceilings. He reported that, at 2035, tower recalled light and medium fixed wing aircraft. From 2040 to 2050, he continued to monitor the weather conditions, and from 2050 to 2055, a brief, heavy shower moved through, reducing visibility to between 1 and 2 statute miles. An H60 helicopter pilot, who was transitioning from south to north on the Avon Park Range between 2030 and 2100, reported that the weather was "worse than briefed." He stated that his aircraft flew through numerous rain showers with visibilities between 1 and 2 miles. At 2015, while arriving at AGR, they experienced "0 – 0" conditions (zero ceiling and visibility) over the field. After slowing the aircraft, he was able to regain contact with the ground and land. Another Patriot Technologies Group aircraft was airborne on the Avon Park Range at the time of the accident. He attended the mass briefing prior to the flight and recalled that, during the briefing, there was no mention of any precipitation or convective activity throughout the flying period. He departed AGR about 1920 and arrived on station about 1935. He recalled that, the weather "began to change rapidly and deteriorate with weather moving from south to north." He was forced to deviate from the mission to remain in VFR conditions. About 2120, unable to maintain VFR, he elected to abort his mission and land at Avon Park Executive Airport (AVO). At 2130 he attempted to land at AVO, but weather prevented the approach. He held over Sebring Airport (SGF) until about 2200, when he reattempted an approach at AVO. He stated that, he did not "receive any additional weather information throughout the flight" and did not "receive a weather recall." He added that he was in continuous radio contact with the command and control center and was monitoring UHF and VHF guard frequencies during the entire flight. A witness was outside at his residence at the time of the accident. He reported that he lived 1 to 2 miles north of the accident site. He stated the following. It was dark at the time and it had just started sprinkling. He heard the airplane, but did not see it. He described the sound as "at full throttle, like it was pulling out of a dive." He then heard a "thud" sound and he knew the airplane had crashed. He called 911 and told the operator that a plane had crashed between his location and Avon Park. He said that there was no explosion. Immediately after the accident, it started raining hard. He was drenched because he needed to be outside to get good reception on his phone. He did not see the wreckage until the next morning. A second witness was outside, on his back porch, about 3/4 mile from the accident site, at the time of the accident. He was talking on the phone to his daughter. He did not see the airplane or the crash, but he heard the airplane fly near his house. The airplane sounded like it was traveling in a northerly direction. He stated that the airplane sounded normal, and then it sounded like a "dive bomber, rolling into a dive." The engine rpm's increased audibly until he heard the airplane crash. He got off the phone and called 911 because he knew an airplane had crashed. He stated that a "terrible storm" hit a few minutes after the accident, and lasted for about 10 minutes. There was a lot of rain, but no thunder or lightning. The rain was so intense th